Final answer:
The angle that the finally-reflected ray CR makes with the plane of mirror M3 is 0°.
Step-by-step explanation:
The angle that the finally-reflected ray CR makes with the plane of mirror M3 can be determined by applying the law of reflection. According to the law of reflection, the angle of incidence is equal to the angle of reflection. In this case, ray CR is incident on mirror M3 after being reflected by mirrors M2 and M1. Since the angle of incidence at M3 is equal to the angle of reflection at M2, and the angle of incidence at M2 is equal to the angle of reflection at M1, the angle of finally-reflected ray CR with the plane of mirror M3 is equal to the angle of incidence of ray IA on mirror M1.
To find the angle of incidence of ray IA on mirror M1, we can refer to the given information. In the previous question, it was mentioned that an object is 2 meters in front of a flat mirror. Ray 1 from the object travels in a direction toward the mirror and normal to the mirror's surface. Ray 2 from the object travels at an angle of 5° from the direction of ray 1, and it also reflects off the mirror's surface. In this case, ray IA can be considered as ray 1 and the angle made by ray IA with the plane of mirror M1 is 0°. Therefore, the angle that the finally-reflected ray CR makes with the plane of mirror M3 is also 0°.